Apparatus for protection of a gas jet generator

ABSTRACT

A gas jet generating apparatus has a container with an electric arc chamber from which the gas jet is to issue, two arc electrodes are provided in the chamber, and at least one of the electrodes has a metallic portion defining a foot-point locality for the arc. The combination of a protective device has near at least one of the electrodes, a vaporizable means of material different from that of said electrode portion so as to effect, when burning off, a change in spectral distribution of the gas jet. Also provided is a signal generating arrangement that is responsive to the spectral distribution for deriving a signal from the change.

United States Patent [1 1 Schafer s41 APPARATUS FOR PROTECTION OF A GAS JET GENERATOR Inventor: (ierd Schal'er, Erlangcn. (icrmzmy I73] Assignee: Siemens Aktiengesellschaft, Berlin/ Munich,Germany 22 Filed: Oct. 29, 1910 [21] Appl. No.: 85,118

3,359,734 12/1967 Ferrie et al. ....60/203 3,308,623 3/1967 7 Ferrie et al, ..60/203 3,038,306 6/1962 Loft ..60/3909 R 2,797,336 6/1957 Loft ..60/39.09 R

[451 May 29, 1973 3,504,490 Klamm ..60/39.09 R

FOREIGN PATENTS OR APPLICATIONS [57] ABSTRACT A gas jet generating apparatus has a container with an electric arc chamber from which the gas jet is to issue, two arc electrodes are provided in the chamber, and at least one of the electrodes has a metallic portion defining a foot-point locality for the arc. The combination of a protective device has near at least one of the electrodes, at vaporizable means of material different from that of said electrode portion so as to effect, when burning off, a change in spectral distribution of the gas jet. Also provided is a signal generating arrangement that is responsive to the spectral distribution for deriving a signal from the change.

13 Claims, 2 Drawing Figures 1 l l I I I l l l l l l I l l I I I l I I I l I l l I I l I PATENIED m2 9 m5 SHEET 1 [II 2 KSUUFIBE IIF IGIII'IIUN BLOCKING BIAS I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 LEA A PATENIEL HLYZQ 1975 saw 2 OF 2 APPARATUS FOR PROTECTION OF A GAS JET GENERATOR My invention relates to protection equipment for a gas jet generator in which the jet is produced by means of an electric arc and issues the jet from an arc chamber. At least one of the foot-point localities of the arc lies on a metal part of an electrode.

A plasma burner with an arc chamber is known from German published patent application 1,271,852. A cup electrode is provided which extends into the chamber of this plasma burner. During operation, the arc burns from this cup electrode into a hollow cylinder electrode under a tangential directed gas supply. In the arc chamher, there is formed a flow cylinder and, in the cup electrode, there is formed a double flow with an axial component. By means of this flow phenomenon the arc is gas vaporized. In such an apparatus for generating a gas jet, one of the two electrodes, preferably the cup electrode, is arranged so as to be adjustable in axial di rection.

As a rule, the electrodes are made of copper and are provided with a liquid cooling arrangement, preferably a water cooling system. Magnetic coils arranged axially and about the respective electrodes serve to rotate the arc. The coolant then passes through the intermediate space between the electrode jacket and the magnetic coil and also protects the electrical insulation of the coils from the high temperature of the arc.

' During operation, the arc slowly burns off the copper of the electrode jacket at the foot-point locality. As soon as the electrode jacket burns through, the cooling water can exit through the opening of the defective electrode jacket. The steam is then transported with the gas jet out of the exit nozzle of the burning chamber and so contaminates the exiting 'gas jet. In addition, the water vaporizes from the heat of the arc in the cooling channel. Because of the gas pressure, the cooling water is moved from the burnt-through location, so that other parts, especially the magnetic coils, can become damaged. The energy supply of the apparatus must be dis connected as soon as possible before a burn-through of an electrode. I

j It is an object of my invention to prevent the burnthrough of an electrode and to protect valuable parts of the equipment from damage bythe arc. Subsidiary to this'object, it is an object of my invention to provide an apparatus for protecting a gas jet generator.

' It is another object of my invention to'provide a gas jet generator equipped with a protective device for protecting parts of the generator from damage by the arc generator in thearc chamber of the apparatus.

To this end, and according to the invention, I provide the electrode at least in the region near the foot-point locality of the arc with a means that, when burned, changes'the spectral distribution of the gas jet. From this deviating spectral distribution, a signal for disconnecting the current supply of the arc is derived. Suitable for this purpose are for example aluminum and chrome. In general, it is advisable to provide a copper electrode with a metal jacket having good heat conductivity at the side of the electrode where the water coolant runs. The metal jacket'extends over the region of the electrode where, from experience, it can be expected that the electrode wall will burn through. The jacket can be made for example from aluminum or an aluminum alloy especially Dural. When the copper electrode burns through, a portion of the jacket is vaporized by the arc and transported by the gas jet. If required, non-metallic materials can also be used, for example, sodium salt or a material containing sodium. This material can be disposed between the parts of a double-walled electrode.

The material vaporized at the foot-point locality causes a characteristic discoloration of the exiting gas jet. An optical interference filter having a pass region optimized for the wavelengths of the emission lines to be measured is provided. By means of this interference filter, this wavelength range is filtered out and directed to a photoelectronic component as an optical signal. The signal, which is in turn provided by this component, is supplied via an amplifier to the electric power supply means of the gas jet apparatus; this signal can for example act upon the blocking grid (gate) of the thyristors of an electronic alternating or polyphase current control for controlling the power. Or, the signal can be used to open the breaker of the apparatus.

Also suitable as photosensitive components, are photoresistors that are connected together in the form of a wheatstone bridge. The change in the bridge current serves as a signal for disconnecting the apparatus.

In addition the filtered radiation can be directed to active photoelements whose sensitivity for the wavelengths of the radiation directed to these elements is sufficient for generating a photo current that can be used for disconnecting the current supply.

The invention will now be described with reference to the drawing wherein:

FIG. 1 illustrates an apparatus for the protection of the gas jet generator according to the invention; and

FIG. 2 illustrates an electrode of the arc chamber of FIG. 1 equipped with an intermediate coating of material having a color spectrum with pronounced emission lines at wavelengths different from the emission-line wavelengths of the electrode material proper.

Referring to FIG. 1, cylinder electrode 2 and a cup electrode 4 are respectively connected to the output of a rectifier 6 equipped with uncontrolled electronic valves (diodes) 8. The diodes 8 being ratedfor a current of approximately 850 amperes at a directcurrent voltage of 700 volts. For controlling the input alternating current of the rectifier 6, there is provided an electronic polyphase current controller 10 having electric valves such as thyristors 12. The controller 10 is con nected to a three phase line having an alternating voltage of, for example, 380 volts via a main switch 14. The thyristors 12 of the controller 10 are connected to an ignition grid control device 15 having an electronic grid blocking stage 16. The control device 15 serves to ignition control the thyristors 12. The control device 15 can, for example, receive its signal for displacing the ignition pulses from a regulating apparatus with a current regulator 17 of which one input is specified by-a current pilot (actual-current) magnitude from a current transformer 18 and of which the second input 19 is specified by a current datum magnitude.

The electrodes 2 and 4 are arranged in arc chamber 20. Preferably, one of the electrodes, for example the cup electrode .4, is movable in axial direction, this direction being the direction of the gas jet 24 formed in the chamber and exiting through an exit nozzle 22 illustrated in FIG. 1 as a Laval nozzle. Coaxial to the two electrodes 2 and 4, are arranged respective field coils 28 and 29. The coils contain hollow conductors through which flow a cooling liquid. I-Iollow conductors 30 are surrounded by an insulating layer 31. For example, the hollow conductors 30 can be imbedded in an insulating layer 31 of casting resin. The electrodes are provided with liquid cooling as represented in the drawing by the arrows. The coolant, such as water, flows through the space between the field coils and the electrodes, the latter being for example made of copper.

The electrodes 2 and 4 are provided with respective linings 33 and 34 made of aluminum or a material containing aluminum preferably Dural. The lining is on the electrodes on the side thereof away from the surface of the electrode upon which the arcs impinge. As soon as an electrode burns through, the aluminum vaporizes at the damaged location and changes the color of the exiting gas jet 24. The aluminum has pronounced emission lines at wavelengths of 0.394 microns and 0.961 microns, whereas the copper, in an adequate range above and below these wavelengths, exhibits no pronounced emission line. These emission lines are directed via a filter 38, a collection lens 40 having a diameter determining to the light intensity, and a diaphragm 42 to a photosensitive electronic component. The pass region of the interference filter 38 is restricted to the wavelengths of the emission lines of the aluminum to be measured. Consequently, the photoelement 44 receives radiation as soon as the exiting gas jet 24 transports vaporized aluminum of the linings 33 or 34 through the exit nozzle 22. One terminal of the photoelement 44 is connected to ground or zero potential. A signal is formed in response to the emission lines of the vaporized aluminum and is directed via an amplifier 46 of the grid blocking stage 16. The power supplied to the arcing chamber is thereby disconnected before the arc cuts through the aluminum coating 33 or 34. Should the latter occur, water vapor could exit through the opening cut by the are. In addition, the field coil 28 and/or 29 could be damaged.

A silicon photocell could be used for the photoelement 44 having a sensitivity region covering the wavelength of 0.394 microns. In addition, a solar cell is suitable for the mentioned wavelength. The sensitivity of such a cell is optimized such that the photo-current becomes a maximum when irradiated with a light having a spectral distribution corresponding to that of sun light outside of the atmosphere. These cells still have a good sensitivity at a wave length of 0.39 microns. In apparatus according to the invention, it is preferable to use a solar cell that has a high sensitivity optimized for blue light.

Also suitable as a photocell 44, is a gallium-arsenide luminescent diode connected as a radiation detector.

In the illustrated embodiment of FIG. 1, there is provided for the protection arrangement an aluminum layer or coating of the electrodes in the region at which the arc impinges thereupon. In the event that the location at which the arc impinges upon the electrode wanders, it is preferable to provide the entire surface of the electrode material facing away from the location at which the arc impinges with a coating. The lining of such a covered electrode can be welded or soldered to the electrode material or it may be shrunk or cast thereupon. The electrode material can be copper for example.

Next to such a metal lining of aluminum, chrome or other suitable material, other elements can be used which correspondingly color the gas jet. Sodium, for

example, has this characteristic. Hence, the surfaceof the electrode facing away from the arc can be provided with a covering containing sodium. In addition, as illustrated in FIG. 2, the electrode material can comprise two like material layers between which is an intermediate layer 50 containing sodium. In this way a coloring of the gas jet is obtained as soon as the first electrode layer burns through. In the event that a material containing sodium is provided on the electrode surface facing away from the arc, there must be provided the condition that the sodium does not come into contact with the cooling water.

If required, an optacal interference filter can be used which has a pass range corresponding to a limited wavelength range of the gas-jet spectrum. The filter is placed between the gas jet and a photosensitive electronic component that is responsive to a spectral change outside the limited range. Circuit means are connected to the component for disconnecting the power from the electrodes in the arc chamber in response to the spectral change.

While the invention has been described by means of a specific example in a specific embodiment, I do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

I claim:

1. With gas jet generating apparatus having a container with an electric arc chamber from which the gas jet is to issue, two are electrodes in said chamber, at least one of said electrodes having a metallic portion defining a foot point locality for the arc, the combination of a protective device comprising vaporizable means disposed adjacent the metallic portion of at least one of said electrodes for giving off a vapor when burned by the arc, said vaporizable means being made of material different from that of said metallic portion so as to effect, when burning off, a change in spectral distribution of the gas jet, and signal generating means responsive to said spectral distribution for deriving a signal from said change.

2. Gas jet generating apparatus comprising a container with an electric arc chamber from which the gas jet is to issue, two are electrodes in said chamber, arcenergizing current supply said connected to said electrodes and having control means for making and breaking the arc current, said electrodes defining respective foot-point areas for said arc, structural means disposed adjacent at least one of said areas for giving off a vapor when burned by the are, said structural means being made of a material different from that of the electrode proper so as to effect, when burning off, a change in spectral distribution of the gas jet and signal generating means responsive to said spectral distribution and electrically connected to said arc-current control means for breaking said current in response to arc-current spectral change.

3. An apparatus according to claim 1, said vaporizable means of said protective deice device a covering on the electrode surface facing away from the are locality, said covering consisting of said material and having a color spectrum with pronounced emission lines at wavelengths different from the emission-line wavelengths of the electrode material proper.

4. An apparatus according to claim 3, said covering consisting at least partially of aluminum.

5. An apparatus according to claim 1, said vaporizable means of material being formed of layers extending over at least a portion of the electrode surface of said respective two arc electrodes which surface faces away from the arc locality, said layers making each of said electrodes a double-walled structure at said portion of said electrode surface, said material having a color spectrum with pronounced emission lines at wavelengths different from the emissiondine wavelengths of the electrode material proper.

6. An apparatus according to claim 5, said material comprising sodium.

7. An apparatus according to claim 1, said combination comprising layers extending over at least a portion of the electrode surface of said respective two are electrodes, which surface faces away from the arc locality, said layers making each of said electrodes a doublewalled structure at said portion of said electrode surface, a coating disposed intermediate said electrodes and said layers, said material having a color spectrum with pronounced emission-lines at wavelengths different from the emission-line wavelengths of the electrode material proper.

8. An apparatus according to claim 7, said material comprising sodium.

9. In an apparatus according to claim 1, said apparatus including power supply means connected to said are electrodes, and said signal generating means comprising a photosensitive electronic component for providinga signal change in response to changes in light intensity, an optical interference filter disposed in the path of the light of said gas jet and adapted to pass the emission lines of said light corresponding to the wavelengths of said material to said component, whereby said signal change is provided in response to a change in the intensity of said emission lines, and circuit means connected to said component for disconnecting said power supply means from said electrode in response to said signal change.

10. In an apparatus according to claim 9, said circuit means comprising a controller connected to said power supply means for controlling the power supplied to said electrodes, said controller including a grid blocking stage, and electric valves connected to said stage for controllingthe flow of said power to said electrodes, said grid blocking stage being connected to said component, whereby said grid blocking stage actuates said valves for interrupting the flow of said power to said electrodes in response to said signal change.

1 1. In an apparatus according to claim 1, said apparatus including power supply means connected to said arc electrodes, and said signal generating means comprising a photosensitive electronic component, an optical interference filter disposed between said gas jet and said component, said filter having a pass band range corresponding to a limited wavelength range of the gasjet spectrum, and said component being responsive to a spectral change outside said range, and circuit means connected to said component for disconnecting said power supply means from said electrodes in response to said change.

12. In an apparatus according to claim 11, said circuit means comprising a controller connected to said power supply means for controlling the power supplied to said electrodes, said controller including a grid blocking stage, and electric valves connected to said stage for controlling the flow of said power to said electrodes, said grid blocking stage being connected to said component, whereby said grid blocking stage actuates said valves for interrupting the flow of said power to said electrodes in response to said signal change.

13. Gas jet generating apparatus comprising a container with an electric arc chamber from which the gas jet is to issue, two are electrodes in said chamber, magnetic field coil means surrounding said electrodes for rotating the arc, arc-energizing current supply means connected to said electrodes and having control means for making and breaking the arc current, said electrodes defining respective foot-point areas for the arc, vaporizable means disposed adjacent at least one of said areas for giving off a vapor when burned by the are after the arc penetrates the electrode, said vaporizable means being made of a material different from that of the electrode proper so as to effect, when burning off, a change in spectral distribution of the gas jet and signal generating means responsive to said spectral distribution and electrically connected to said arc-current control means for breaking said current in response to said spectral change, thereby extinguishing the arc before the arc causes damage to said coil means. 

1. With gas jet generating apparatus having a container with an electric arc chamber from which the gas jet is to issue, two arc electrodes in said chamber, at least one of said electrodes having a metallic portion defining a foot point locality for the arc, the combination of a protective device comprising vaporizable means disposed adjacent the metallic portion of at least one of said electrodes for giving off a vapor when burned by the arc, said vaporizable means being made of material different from that of said metallic portion so as to effect, when burning off, a change in spectral distribution of the gas jet, and signal generating means responsive to said spectral distribution for deriving a signal from said change.
 2. Gas jet generating apparatus comprising a container with an electric arc chamber from which the gas jet is to issue, two arc electrodes in said chamber, arc-energizing current supply means connected to said electrodes and having control means for making and breaking the arc current, said electrodes defining respective foot-point areas for said arc, structural means disposed adjacent at least one of said areas for giving off a vapor when burned by the arc, said structural means being made of a material different from that of the electrode proper so as to effect, when burning off, a change in spectral distribution of the gas jet and signal generating means responsive to said spectral distribution and electrically connected to said arc-current control means for breaking said current in response to said spectral change.
 3. An apparatus according to claim 1, said vaporizable means of said protective device comprising a covering on the electrode surface facing away from the arc locality, said covering consisting of said material and having a color spectrum with pronounced emission lines at wavelengths different from the emission-line wavelengths of the electrode material proper.
 4. An apparatus according to claim 3, said covering consisting at least partially of aluminum.
 5. An apparatus according to claim 1, said vaporizable means of material being formed of layers extending over at least a portion of the electrode surface of said respective two arc electrodes which surface faces away from the arc locality, said layers making each of said electrodes a double-walled structure at said portion of said electrode surface, said material having a color spectrum with pronounced emission lines at wavelengths different from the emission-line wavelengths of the electrode material proper.
 6. An apparatus according to claim 5, said material comprising sodium.
 7. An apparatus according to claim 1, said combination comprising layers extending over at least a portion oF the electrode surface of said respective two arc electrodes, which surface faces away from the arc locality, said layers making each of said electrodes a double-walled structure at said portion of said electrode surface, a coating disposed intermediate said electrodes and said layers, said material having a color spectrum with pronounced emission-lines at wavelengths different from the emission-line wavelengths of the electrode material proper.
 8. An apparatus according to claim 7, said material comprising sodium.
 9. In an apparatus according to claim 1, said apparatus including power supply means connected to said arc electrodes, and said signal generating means comprising a photosensitive electronic component for providing a signal change in response to changes in light intensity, an optical interference filter disposed in the path of the light of said gas jet and adapted to pass the emission lines of said light corresponding to the wavelengths of said material to said component, whereby said signal change is provided in response to a change in the intensity of said emission lines, and circuit means connected to said component for disconnecting said power supply means from said electrode in response to said signal change.
 10. In an apparatus according to claim 9, said circuit means comprising a controller connected to said power supply means for controlling the power supplied to said electrodes, said controller including a grid blocking stage, and electric valves connected to said stage for controlling the flow of said power to said electrodes, said grid blocking stage being connected to said component, whereby said grid blocking stage actuates said valves for interrupting the flow of said power to said electrodes in response to said signal change.
 11. In an apparatus according to claim 1, said apparatus including power supply means connected to said arc electrodes, and said signal generating means comprising a photosensitive electronic component, an optical interference filter disposed between said gas jet and said component, said filter having a pass band range corresponding to a limited wavelength range of the gas-jet spectrum, and said component being responsive to a spectral change outside said range, and circuit means connected to said component for disconnecting said power supply means from said electrodes in response to said change.
 12. In an apparatus according to claim 11, said circuit means comprising a controller connected to said power supply means for controlling the power supplied to said electrodes, said controller including a grid blocking stage, and electric valves connected to said stage for controlling the flow of said power to said electrodes, said grid blocking stage being connected to said component, whereby said grid blocking stage actuates said valves for interrupting the flow of said power to said electrodes in response to said signal change.
 13. Gas jet generating apparatus comprising a container with an electric arc chamber from which the gas jet is to issue, two arc electrodes in said chamber, magnetic field coil means surrounding said electrodes for rotating the arc, arc-energizing current supply means connected to said electrodes and having control means for making and breaking the arc current, said electrodes defining respective foot-point areas for the arc, vaporizable means disposed adjacent at least one of said areas for giving off a vapor when burned by the arc after the arc penetrates the electrode, said vaporizable means being made of a material different from that of the electrode proper so as to effect, when burning off, a change in spectral distribution of the gas jet and signal generating means responsive to said spectral distribution and electrically connected to said arc-current control means for breaking said current in response to said spectral change, thereby extinguishing the arc before the arc causes damage to said coil means. 